1. Field of the Invention
The present invention is directed to a communication means in an electrographic printer or copier device. A plurality of function units such as a fixing station, a character generator, a paper transport means, a central control unit, etc., are contained in an electrographic printer or copier device. Over and above this, there are numerous smaller function units such as, for example, sensors, motors, switches, keys, etc. The functionality of all of these function units must be coordinated for the operation of the printer or copier device.
2. Description of the Related Art
Bus systems that are controlled via a main module HM are utilized in known printer or copier devices for the coordination of approximately 100 sensors and approximately 40 power consuming units. The structure of such a known control system may be seen from FIG. 1. The signal transmission between the main module HM and the sub-modules SUB1 . . . SUBn ensues via a first bus system BBUS. One sub-module SUB1 . . . SUBn controls power consumers LV, acquires data from sensors, and exchanges data and messages with other sub-modules SUB1 . . . SUBn. The power consumers LV are directly controlled by the sub-modules SUB1 . . . SUBn via individual lines, and sensor assemblies SPU1 . . . SPUn for editing the information acquired by the sensors are inserted between the sub-module SUB1 . . . SUBn and individual sensors ES. The sub-modules SUB1 . . . SUBn communicate with the sensor assemblies via second bus system VBUS. The second bus system VBUS can, for example, be a coupling with a parallel V24 interface. The communication between the sensor assemblies and the sub-modules ensues on the basis of what is referred to as a polling method wherein a submodule SUB1 . . . SUBn interrogates desired data from a sensor assembly SPU1 . . . SPUn. The communication between the sub-modules SUB1 . . . SUBn also ensues according to this polling method, whereby the main module HM can be viewed as a master and the sub-modules SUB1 . . . SUBn can be viewed as slaves.
The data traffic between the individual sub-modules SUB1 . . . SUBn can thereby only be sequenced in dialog traffic between the sub-modules SUB1 . . . SUBn and the main module HM. This, for example, means that a message of a sensor ES to a sub-module SUBn must be communicated from this sub-module SUBn to the main module HM and from the latter to the other sub-module SUB1 . . . SUB3. Over and above this, synchronous control commands can only be transmitted asynchronously to the individual submodules SUB1 . . . SUBn.
In addition to the long program running time, the known interrogation method also causes an increased wiring outlay since parallel wiring is required. The efficiency of the interrogation method is also low because conditions that have not changed since the preceding interrogation are frequently interrogated. The data traffic, which can only be sequenced between the master and slave, is coordinated with a priority control by a single control unit contained in the main module HM. Delays in the function execution of the printer or copier device can thus occur. This fact is countered in that fast signal changes are handled with what is referred to as a parallel port interrogation.